Experimental study and finite element modelling of the torsional behavior of self-compacting reinforced concrete (SCRC) beams strengthened by GFRP

The present study experimentally and numerically investigates the behavior of ten self-compacting reinforced concrete (SCRC) beams strengthened by various means of externally bonded glass fiber reinforced polymer (GFRP) strips and subjected to pure torsion. The experimental matrix is designed to explore the impact of the number of GFRP layers, the width of the strengthening layers, and the spacing between those layers on the ultimate torsional capacity, the ultimate angle of twist, ductility, and failure patterns with respect to an un-strengthened specimen. Tests revealed that the specimen that was strengthened along its whole length using three layers of GFRP sheets yielded the highest gain in the ultimate torsional moment of 33.3% compared to the un-strengthened specimen. Additionally, the highest gain in the energy dissipation capacity among all strengthened beams (209.4% higher than the control beam) was obtained when four layers of GFRP sheets spaced every 300 mm were installed. Moreover, a three-dimensional (3D) non-linear finite element analysis is carried out via ABAQUS software to predict the torsional characteristics of SCRC beams either strengthened by GFRP strips or kept bare. The numerical model well captured the failure patterns, torque versus angle of twist responses, stress distribution, and the ultimate load of SCRC beams strengthened by GFRP strips with respect to the experimental findings.